Radio receiving system



Dec. 9, 1930.

A F. VAN DYCK RADIO RECEIVING SYSTEM Filed Sept. 15, 1926 luwl 7 m m I 122211 17 wmxr 16 mm g h S w Z 1] E I '1 q s INVENTOR.

ARTHUR F. VANDYCK ATTORNEY Patented Dec. 9, 1930 UNITED TATES ATENT OFFICE ARTHUR I. VAN DYCK, 0F YONKERS, NEW YORK, ASSIGNOR TO RADIO CORPORATION OF AMERICA, A CORPORATION OF DELAEVARE RADIO RECEIVING SYSTEM Application filed September 15, 1926. Serial No. 135,497.

My invention relates to radio receiving systems and particularly to receiving systems embodying an electro-static loud speaker de- V1C6.' I I 1 An object of my invention is to provide a radio responsive system adapted to cooperate with an electro-static loud speaker device.

7 Another object of my invention is to pro- Vide a radio responsive device adapted to change signal modulated radio frequency energy from signal frequency to optimum frequency for an electrostatic loud speaker device.

The usual radio receiving systems operate at a disadvantage because of the fact that rectification or detection of the received signals is necessary before the usual signal receiver can be operated. Such detection is accompanied by an undesirable distortion which destroys to some extent the true character of the signals. I have found that the so-called electro-static loud speaker which has been known in a rudimentary form in the prior art, but has heretofore been operated only by audio frequency currents such as those produced by a radio detector, will also respond at an audible frequency, to radio frequencies which are modulated at an audio frequency, and reproduce the sound corresponding to the modulation frequency.

' I have also found that for most practicable operation of an electro-static loud speaker that it must be supplied with energy in certain preferred forms and conditions, and that the loud speaker should desirably be combined with a radio responsive system especially adapted to provide energy in the proper form for it.

The electro-static loud speaker consists essentially of an electrical condenser in which provision is made for vibration of a condenser plate, under the influence of the electro-st'atic attraction of an electric charge upon the plates, the vibration of the plate being caused to produce air vibrations, for sound. The electric charge may be caused to vary directly at an'audible frequency to whichthe vibratory plate can respond, or the energy may be impressed in the form of modulated radio frequency energy, in which case the vibratory plate is unable to respond to the radio frequency vibrations but can respond to the modulations impressed upon the radio frequency vibrations. This is because the attraction between charged plates does not vary linearly With charge, so that a component of force varying at modulation frequency is produced by modulated radio frequency. The latter system is preferable in a radio receiving system for reasons herein disclosed. T Vhen so used the magnitude of the response of the loud speaker, in producing sound corresponding to the audio frequency modulations, is determined by the amplitude of the radio oscillations impressed.

For instance, the electrostatic loud speaker may be connected across a tuning element inan antenna circuit at a point of maximum potential. This connection, however, is unsatisfactory because the energy available in the antenna circuit is small, lacking amplification. A better response from the electro-st'atic loud speaker may be obtained by interposing a typical'triode amplifier system between the antenna system and the loud speaker, thereby increasing the amplitude of the oscillations.

A. superior response of the electrostatic loud speaker may sometimes be secured by reducing the radio frequency, as well as increasing its amplitude, by the interposition not only of a typical triode amplifier system but also of a heterodyning system to reduce the radio frequency oscillations to a lower radio frequency to which the loud speaker will under certain circumstances respond more efiectively. Also the difficulties of securing high degrees of amplification are lessened.

A further gain in response of the loud speaker may be obtained from an amplifying and heterodyning system, by refiexing the lower radio frequency 'through the tri-- odes provided for the amplification of the higher radio frequency. 7 I

By this construction, energy in a proper form is supplied to an electro-static loud speaker device to obtain a maximum sound volume therefrom. The energy is further obtained without the intervention of a detector or rectifier device, thereby avoiding 7 of a superior embodiment ofmy invention.

Figure 3 is a diagrammatic representation of circuits and apparatus representing a preferred embodiment of 1 y invention.

Referring to Figure 1, I-provide ans-antenna system 1, a radio frequency amplifier 2, having a tuned input circuit 3 and atuned output circuit 1:, and an electrostatic loud speaker device 5. By this device the incoming signal frequency is receivedby the a11- tenna 1,transferred to the input circuit 3, amplified by the amplifier 2 and fed to the output circuit 4'. Circuit 4 being tuned to the incoming radio frequency of the signal, maximum oscillation voltage at the modula'ted signal frequencyisnnpressed upon the loud speaker 5 and a superior sound response is obtained than would be obtained from the device if it were connected directly .tothe antenna circuit. 7

Referring to Figure 2 I provide as before an antenna-system 1, and a radio frequency amplifier 2 having a tuned input circuit 3.

I further provide a heterodyning means 6 connected thereto and supplied with steady oscillatory energy at a frequency difiering from that of the signal frequency by an amount equal to another radio frequency, from a generator 7. I provide an output circuit 8 connected to the heterodyning device and tuned to theheterodyne beat frequency. An electro-static loud speaker 5 is connected to the tuned circuit 8. By this means I supply to the electro-static loud speaker device a substantial amplitude of modulated radio frequency energy at an optimum frequency, the frequency of the source 7 beingchosen to differ from the incoming signal frequency 7 by an amount above the highest audible frequency. By this means the electro-static loud speaker is supplied with a substantial amount of modulated radio frequency energy at an optimum frequency.

Referring toyFigure u I show a system whereby maximum utilization ofthe triodes As before, I proof an amplifier is made. I vide anantenna system lcoupled to the tuned input circuit 3 of a radio frequency amplis fier 2. The amplifier 2 may consist of a triode 9 having anvoutput transformer-111,

associated with a second triode 12 having a second output transformer 14, in turn associated with a heterodyning device 6. The heterodyning device 6 may desirably consist of a triode 15 and a feed-back transform er coupling device 16. The output circuit of the triode 15 is connected to a tuned reflexing transformer device 17 which is connected between the tuned input circuit 3 and the triode 9. Means are provided in thetransformor 11 for the transferring of energy at the original signal frequency and also at the heterodyne frequency. A second output transformer 18 is provided in the output circuit of the triode 12. The transformer 18 has its secondary circuit tuned to the beat frequency and connected to the electro-static loud speaker device 5. i

By the embodiment of my invention shown in Figure 3 signals are received upon the antenna system 1, transferred to the input circuit 3, amplified by the triode 9, transferred by the coupling transformer llto the triode 12, and amplified therein. Signals, still at the original frequency, are transferred from the triode 12 by the coupling transformer 14 to the triode 15. The triode 15 is caused to generate oscillations by the feed-back trans former 16, at a proper frequency for the production of abeat frequency. The signal-modulations atthe beat frequency are transferred through the. reflexing transformer 17150 the grid circuit of the triode 9, amplified therein, independently of the signals at the ori 'nal higher signal frequency, transferred t erefrom through the transformer 11, to thetriode 12, again amplified therein, independently of the signals at the original frequency,

and transferred through the output transformerto the electro-static loud speaker de.-- vice 5. The secondary circuit of the output transformer 18 is-tuned to the beat frequency and an optimum amount of energy at an optimum amplitude is thus impressed upon the electro-static loud speaker'5.

It is to be noted that the operation of rectification or detection does not occur at any point in the transfer of the signals to the loud speaker device and that, therefore, distortion necessarily inherent in all detection processes is avoided. V

- While I have shown but three embodiments of my invention in the foregoing drawings anddescriptions it is capable of. various modifications therefrom without departing from the spirit thereof, and it is desired therefore that only suchlimitations shall be imposed thereon as are required by the prior art 0 indicated by the appended claim. j

I claim as m invention: V Apparatus or reproducing sound from a modulated radio frequency signal comprisin a circuit energized by said-signal, a 100 source of energy, amplifying and detecting means for obtaining an amplified superaudible beat frequency from said signal and the energy from said local source, a tuned circuit connected to the output of said amplifying and detecting means for obtaining a resonance potential rise, said tuned circuit consisting of an inductive reactance element and a capacitive reactance element connected in parallel, and an electrostatic loud-speaker connected across the terminals of one of the reactance elements whereby the maximum potential obtained by said resonance potential rise is applied across the electrostatic loudspeaker terminals and the electrostatic loudspeaker functions as a detector to reproduce sound from said superaudible beat frequency.

ARTHUR F. VAN DYOK. 

